Mushroom poisoning is poisoning resulting from the ingestion of mushrooms that contain toxic substances. Symptoms can vary from slight gastrointestinal discomfort to death in about 10 days. Mushroom toxins are secondary metabolites produced by the fungus.

Mushroom poisoning is usually the result of ingestion of wild mushrooms after misidentification of a toxic mushroom as an edible species. The most common reason for this misidentification is a close resemblance in terms of color and general morphology of the toxic mushrooms species with edible species. To prevent mushroom poisoning, mushroom gatherers familiarize themselves with the mushrooms they intend to collect, as well as with any similar-looking toxic species. The safety of eating wild mushrooms may depend on methods of preparation for cooking. Some toxins, such as amatoxins, are thermostable and mushrooms containing such toxins will not be rendered safe to eat by cooking.

Signs and symptoms

Poisonous mushrooms contain a variety of different toxins that can differ markedly in toxicity. Symptoms of mushroom poisoning may vary from gastric upset to organ failure resulting in death. Serious symptoms do not always occur immediately after eating, often not until the toxin attacks the kidney or liver, sometimes days or weeks later.

The most common consequence of mushroom poisoning is simply gastrointestinal upset. Most "poisonous" mushrooms contain gastrointestinal irritants that cause vomiting and diarrhea (sometimes requiring urgent care), but usually no long-term damage. However, there are a number of recognized mushroom toxins with specific, and sometimes deadly, effects:

{| class="wikitable"

|-

! Toxin

! Toxicity

! Effects

|-

| α-Amanitin

| Deadly

| Causes often fatal liver damage 1–3 days after ingestion. The principal toxin in the death cap.

|-

| Phallotoxin

| Non-lethal

| Causes extreme gastrointestinal upset. Found in various mushrooms.

|-

| Orellanine

| Deadly

| Redox cycler similar to paraquat. Causes kidney failure within three weeks after ingestion. Principal toxin in genus Cortinarius.

|-

| Muscarine

| Non-lethal

| Causes Cholinergic crisis. Found in various mushrooms. Antidote is atropine.

|-

| Monomethylhydrazine (MMH)

| Deadly

| Causes brain damage, seizures, gastrointestinal upset, and hemolysis. Metabolic poison. Principal toxin in genus Gyromitra. Antidote is large doses of intravenous pyridoxine hydrochloride.

|-

| Coprine

| Non-lethal

| Causes illness when consumed with alcohol. Principal toxin in genus Coprinus.

|-

| Ibotenic acid

| Non-lethal

| Excitotoxin. Principal toxin in Amanita muscaria, A. pantherina, and A. gemmata.

|-

| Muscimol

| Non-lethal

| Causes CNS depression and hallucinations. Principal toxin in Amanita muscaria, A. pantherina, and A. gemmata.

|-

| Arabitol

| Non-lethal

| Causes diarrhea in some people.

|-

| Bolesatine

| Non-lethal

| Causes gastrointestinal irritation, vomiting, nausea.

|-

| Ergotamine

| Deadly

| Affects the vascular system and can lead to loss of limbs and/or cardiac arrest. Found in genus Claviceps.

|}

The period between ingestion and the onset of symptoms varies dramatically between toxins, some taking days to show symptoms identifiable as mushroom poisoning.

  • α-Amanitin: For 6–12 hours, there are no symptoms. This is followed by a period of gastrointestinal upset (vomiting and profuse watery diarrhea). This stage is caused primarily by the phallotoxins and typically lasts 24 hours. At the end of this second stage is when severe liver damage begins. The damage may continue for another 2–3 days. Kidney damage can also occur. Some patients will require a liver transplant. Amatoxins are found in some mushrooms in the genus Amanita, but are also found in some species of Galerina and Lepiota. Recently, Silybum marianum or blessed milk thistle has been shown to protect the liver from amanita toxins and promote regrowth of damaged cells.
  • Orellanine: This toxin generally causes no symptoms for 3–20 days after ingestion. Typically around day 11, the process of kidney failure begins, A related toxin that causes similar symptoms but within 3–6 days has been isolated from Amanita smithiana and some other related toxic Amanitas.
  • Muscarine: Muscarine stimulates the muscarinic receptors of the nerves and muscles. Symptoms include sweating, salivation, tears, blurred vision, palpitations, and, in high doses, respiratory failure. Muscarine is found in mushrooms of the genus Omphalotus, notably the jack o' Lantern mushrooms. It is also found in A. muscaria, although it is now known that the main effect of this mushroom is caused by ibotenic acid. Muscarine can also be found in some Inocybe species and Clitocybe species, in particular Clitocybe dealbata, and some red-pored Boletes.

Causes

thumb|Immature, possibly poisonous, [[Amanita mushrooms]] thumb|Edible shaggy mane [[Coprinus comatus mushrooms]]

thumb|Two examples of immature [[Amanitas, one deadly and one edible]] thumb|An edible [[puffball which closely resembles the immature Amanitas]]

thumb|[[Omphalotus olearius|Jack-O-Lantern, a poisonous mushroom sometimes mistaken for a chanterelle]]

thumb|"[[Chanterelle", edible]]

New species of fungi are continuing to be discovered, with an estimated number of 800 new species registered annually. This, added to the fact that many investigations have recently reclassified some species of mushrooms from edible to poisonous has made older classifications insufficient at describing what now is known about the different species of fungi that are harmful to humans. It is now thought that of the approximately 100,000 known fungi species found worldwide, about 100 of them are poisonous to humans. However, by far the majority of mushroom poisonings are not fatal, and the majority of fatal poisonings are attributable to the Amanita phalloides mushroom.

A majority of these cases are due to mistaken identity. they have been mistaken for Coprinus comatus. In this case, the victim had some limited experience in identifying mushrooms, but did not take the time to correctly identify these particular mushrooms until after he began to experience symptoms of mushroom poisoning.

The author of Mushrooms Demystified, David Arora cautions puffball-hunters to beware of Amanita "eggs", which are Amanitas still entirely encased in their universal veil. Amanitas at this stage are difficult to distinguish from puffballs. Foragers are encouraged to always cut the fruiting bodies of suspected puffballs in half, as this will reveal the outline of a developing Amanita should it be present within the structure.

A majority of mushroom poisonings, in general, are the result of small children, especially toddlers in the "grazing" stage, ingesting mushrooms found on the lawn. While this can happen with any mushroom, Chlorophyllum molybdites is often implicated due to its preference for growing in lawns. C. molybdites causes severe gastrointestinal upset but is not considered deadly poisonous.

A few poisonings are the result of misidentification while attempting to collect hallucinogenic mushrooms for recreational use. In 1981, one fatality and two hospitalizations occurred following consumption of Galerina marginata, mistaken for a Psilocybe species. Galerina and Psilocybe species are both small, brown, and sticky, and can be found growing together. However, Galerina contains amatoxins, the same poison found in the deadly Amanita species. Another case reports kidney failure following ingestion of Cortinarius orellanus, a mushroom containing orellanine.

It is natural that accidental ingestion of hallucinogenic species also occurs, but is rarely harmful when ingested in small quantities. Cases of serious toxicity have been reported in small children. Amanita pantherina, while containing the same hallucinogens as Amanita muscaria (e.g., ibotenic acid and muscimol), has been more commonly associated with severe gastrointestinal upset than its better-known counterpart. Gyromitra spp., "false morels", are deadly poisonous if eaten raw. They contain a toxin called gyromitrin, which can cause neurotoxicity, gastrointestinal toxicity, and destruction of the blood cells. but it is best to avoid mixing alcohol with other members of this genus.

Recently, poisonings have also been associated with Amanita smithiana. These poisonings may be due to orellanine, but the onset of symptoms occurs in 4 to 11 hours, which is much quicker than the 3 to 20 days normally associated with orellanine.

Paxillus involutus is also inedible when raw, but is eaten in Europe after pickling or parboiling. However, after the death of the German mycologist Dr. Julius Schäffer, it was discovered that the mushroom contains a toxin that can stimulate the immune system to attack its red blood cells. This reaction is rare but can occur even after safely eating the mushroom for many years. Similarly, Tricholoma equestre was widely considered edible and good, until it was connected with rare cases of rhabdomyolysis.

In the fall of 2004, thirteen deaths were associated with consumption of Pleurocybella porrigens or "angel's wings". In general, these mushrooms are considered edible. All the victims died of an acute brain disorder, and all had pre-existing kidney disease. The exact cause of the toxicity was not known at this time and the deaths cannot be definitively attributed to mushroom consumption.

However, mushroom poisoning is not always due to mistaken identity. For example, the highly toxic ergot Claviceps purpurea, which grows on rye, is sometimes ground up with rye, unnoticed, and later consumed. This can cause devastating, even fatal, effects, called ergotism.

Cases of idiosyncratic or unusual reactions to fungi can also occur. Some are probably due to allergy, others to some other kind of sensitivity. It is not uncommon for a person to experience gastrointestinal upset associated with one particular mushroom species or genus.

Poisonous mushrooms

Of the most lethal mushrooms, five—the death cap (A. phalloides), the three destroying angels (A. virosa, A. bisporigera, and A. ocreata), and the fool's mushroom (A. verna)—belong to the genus Amanita, and two more—the deadly webcap (C. rubellus), and the fool's webcap (C. orellanus)—are from the genus Cortinarius. Several species of Galerina, Lepiota, and Conocybe also contain lethal amounts of amatoxins. Deadly species are listed in the List of deadly fungi.

The following species may cause great discomfort, sometimes requiring hospitalization, but are not considered deadly.

  • Amanita muscaria (fly agaric) – Contains the psychoactive muscimol and the neurotoxin ibotenic acid. Ibotenic acid decarboxylates into muscimol upon curing of the mushroom, rendering it relatively non-toxic, though death via respiratory depression is possible. Muscimol intoxication is often considered unpleasant and undesirable however, and as such has seen little recreational use compared to the unrelated psilocybin mushroom, though it has been used as an entheogen by the native people of Siberia.
  • Amanita pantherina (panther mushroom) – contains similar toxins as A. muscaria, but is associated with more fatalities than A. muscaria.
  • Many Inocybe species such as Inocybe fastigiata and Inocybe geophylla contain muscarine.
  • Inosperma erubescens has caused death.
  • Some white Clitocybe species, including C. rivulosa and C. dealbata, contain muscarine.
  • Paxillus involutus (brown roll-rim) – once thought edible, but now found to destroy red blood cells with regular or long-term consumption.

Mushrooms have also been found to have evolved toxicity independently from each other. Researchers have found that different mushroom species share the same type of amatoxin called amanitin. They specifically looked at three of the deadliest species, Amanita, Galerina, and Lepiota. Through genome sequencing, a scientific process that determines the DNA sequence of an organism's genome, they determined that these unrelated mushrooms obtained the genetic information to produce the toxin via horizontal gene transfer. Once assimilated, it can then be passed down to an offspring. The researchers also concluded that there is "an unknown ancestral fungal donor," that allowed for horizontal gene transfer.

Mushroom toxins have appeared and disappeared many times throughout their evolutionary history. If mushrooms are consumed, it can negatively affect their ability to disperse spores, survive, and reproduce. Snails and insects are fungivores and many have learned or evolved to avoid eating poisonous mushrooms. However, it is believed that mammals pose a higher threat to mushrooms than fungivores, as larger body sizes mean they are more capable of eating an entire fungus in one sitting. In the United States, mushroom poisoning kills an average of about 3 people a year. According to National Poison Data System (NPDS) annual reports published by America's Poison Centers, the average number of deaths occurring over a ten-year period (2012–2020) sits right at 3 a year. In 2012, 4 out of the 7 total deaths that occurred that year, were attributed to a single event where a "housekeeper at a Board and Care Home for elderly dementia patients collected and cooked wild (Amanita) mushrooms into a sauce that she consumed with six residents of the home.". Over 1,300 emergency room visits in the United States were attributed to poisonous mushroom ingestion in 2016, with about 9% of patients experiencing a serious adverse outcome.

Society and culture

Folklore

Many old wives' tales concern the defining features of poisonous mushrooms. However, there are no general identifiers for poisonous mushrooms, so such beliefs are unreliable. Guidelines to identify particular mushrooms exist, and will serve only if one knows which mushrooms are toxic.

Examples of erroneous folklore "rules" include:

  • "Poisonous mushrooms are brightly colored." – Indeed, fly agaric, usually bright-red to orange or yellow, is narcotic and hallucinogenic, although no human deaths have been reported. The deadly destroying angel, in contrast, is an unremarkable white. The deadly Galerinas are brown. Some choice edible species (chanterelles, Amanita caesarea, Laetiporus sulphureus, etc.) are brightly colored, whereas most poisonous species are brown or white.
  • "Insects/animals will avoid toxic mushrooms." – Fungi that are harmless to invertebrates can still be toxic to humans; the death cap, for instance, is often infested by insect larvae.
  • "Poisonous mushrooms blacken silver." – None of the known mushroom toxins react with silver.
  • "Poisonous mushrooms taste bad." – People who have eaten the deadly Amanitas and survived have reported that the mushrooms tasted quite good.
  • "All mushrooms are safe if cooked/parboiled/dried/pickled/etc." – While it is true that some otherwise-inedible species can be rendered safe by special preparation, many toxic species cannot be made toxin-free. Many fungal toxins are not particularly sensitive to heat and so are not broken down during cooking; in particular, α-amanitin, the poison produced by the death cap (Amanita phalloides) and others of the genus, is not denatured by heat.
  • "Poisonous mushrooms will turn rice red when boiled." – A number of Laotian refugees were hospitalized after eating mushrooms (probably toxic Russula species) deemed safe by this folklore rule and this misconception cost at least one person her life.
  • "Poisonous mushrooms have a pointed cap. Edible ones have a flat, rounded cap." – The shape of the mushroom cap does not correlate with presence or absence of mushroom toxins, so this is not a reliable method to distinguish between edible and poisonous species. Death cap, for instance, has a rounded cap when mature.
  • "Boletes are, in general, safe to eat." – It is true that, unlike a number of Amanita species in particular, in most parts of the world, there are no known deadly varieties of the genus Boletus, which reduces the risks associated with misidentification. However, mushrooms like the Devil's bolete are poisonous both raw and cooked and can lead to strong gastrointestinal symptoms, and other species like the lurid bolete require thorough cooking to break down toxins. As with another mushroom genera, proper caution is, therefore, advised in determining the correct species.

Notable cases

  • Siddhartha Gautama (known as The Buddha), by some accounts, may have died of mushroom poisoning around ~479 BCE, though this claim has not been universally accepted.
  • Roman Emperor Claudius is said to have been murdered by being fed the death cap mushroom. However, this story first appeared some two centuries after the events, and it is debatable whether Claudius was murdered at all.
  • The best-selling author Nicholas Evans (The Horse Whisperer) was poisoned (but survived) after eating Cortinarius rubellus.
  • The parents of the physicist Daniel Gabriel Fahrenheit, who created the Fahrenheit temperature scale, died in Danzig on 14 August 1701 from accidentally eating poisonous mushrooms.
  • On faulty advice from a friend who was also a doctor, the composer Johann Schobert insisted that certain poisonous mushrooms he had gathered were edible despite the express warning of cooks at two separate restaurants to which he had taken the mushrooms. Schobert ultimately died from consuming the mushrooms, as did his wife, most of their children, their maidservant, the doctor friend, and three other acquaintances.
  • 2023 Leongatha mushroom murders − Australian woman Erin Patterson was found guilty of three murders and one attempted murder of members of her estranged husband's family by serving them beef Wellingtons which contained A. phalloides. Three of the four guests died within days of the meal, while one survived after receiving an organ transplant and spending multiple weeks in a coma.

See also

  • List of deadly fungi (for lethal species only)
  • List of poisonous fungi (including non-deadly species that are nevertheless harmful)
  • Pathogenic fungus

References

  • Poisonous mushrooms: microscopic identification in cooked specimens from medical mycologist R.C. Summerbell
  • Mushroom Poisoning Syndromes from the North American Mycological Association
  • Mushroom Poisoning Case Registry (North America) from the North American Mycological Association
  • American Association of Poison Control Centers Provides information on the toxicity of mushrooms in your area, symptoms and first aid.